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EPR of γ-induced defects and their effects on the photoluminescence in the glasses of the Ag0.05Ga0.05Ge0.95S2-Er2S3 system
Abstract
Paramagnetic defects in erbium-doped γ-irradiated chalcogenide glasses were investigated by EPR method. Vacancy nature of defects and the dependence of their concentration on the irradiation dose and erbium content were determined. The measurement of the static magnetization revealed the presence of paramagnetic and ferromagnetic subsystems caused by isolated Er3+ ions and ion clusters, respectively. PL spectra of 4f-4f transitions of Er3+ ions and the radiation mechanism of γ-irradiated glasses were investigated. It was determined that PL intensity depends on the number of radiation induced defects and on the nature of the distribution of erbium which were determined by EPR and magnetic susceptibility.
... Although the number of reports on the effect of radiation on Er 3+ doped glasses is limited, other materials such as crystals, phosphors, fibers, and glassy alloys have been researched extensively to investigate the changes in their properties. The variations in the optical properties comprise of the appearance of new peaks, decrement in the intensity of the existing absorption peaks due to dissolving of the clusters [13], diminution in the transmittance because of the generation of color centers [11,14], shifting of the cutoff to higher wavelengths [11], and reduction in the optical bandgap due to the increase in the width of the band tails of the localized states [12,15]. M. Stef et al. [13] in BaF 2 :Er 3+ crystal observed a two-fold increase in the green emission and a three-fold increase in the red emission after 270 kGy γ irradiation. ...
... In contrast, the radiation resistance of Er:GSAG crystal irradiated with γ rays was validated by Y. Chen et al. [14] by no significant change in the fluorescence intensity between 2.6 and 3.0 μm at 35 Mrad dose, and no much deterioration even up to 105 Mrad dose. A new band corresponding to the 4 I 9/2 → 4 I 15/2 transition of the Er 3+ ion appeared in Ag 0.05 Ga 0.05 Ge 0.95 S 2 -Er 2 S 3 glassy alloy at 812 nm in the PL spectra after 2000 Gy γ dose [15]. About the space environment, when commercial erbium doped optical fiber was irradiated with 14 Gy dose, M. V. Uffelen et al. [16] found an enlargement in the 1530 nm emission intensity but no significant change in the excited state lifetime. ...
The influence of 0.25–30 kGy γ doses on the 10BaO–20ZnO–20LiF-49.3B2O3-0.7Er2O3 glass was analyzed through the density, optical absorption, thermo-, and photo-luminescence. With a successive increase in the dose, the density of the glass increased, confirming radiation-induced compaction. The color of the glass deepened progressively with the increase in the γ dose, leading to the enhancement in the optical absorption. A continuous fall in the bandgap and an increase in the Urbach energy was also observed. The rise in the electron density with dose, caused a gradual upsurge in the covalency around the Er³⁺ ions, as inferred from the bonding parameter (δ), and the Judd-Ofelt parameters (Ω2,Ω4,Ω6). The defects produced in the glass because of irradiation were evaluated using the trap parameters deduced from the Computerized Glow Curve Deconvolution and Chen's peak shape methods. The 30 kGy irradiated glass contained deeper traps when compared to the 0.25 kGy irradiated glass. The excitation spectrum recorded by monitoring the emission at 550 nm revealed the spectral transitions originating from the ground state ⁴I15/2 of the Er³⁺ ion to ⁴G9/2, ⁴G11/2, (²G,⁴F)9/2, ⁴F5/2, and ⁴F7/2 excited states, among which the ⁴I15/2 → ⁴G11/2 transition at 379 nm was very intense. In the emission spectra, one violet (²H9/2→⁴I15/2) and two green emissions (²H11/2→⁴I15/2 and ⁴S3/2→⁴I15/2) were detected out of which the ⁴S3/2→⁴I15/2 transition was the most prominent. The decrement in the intensity of this emission with dose was attributed to the radiation-induced quenching. The laser performance parameters computed by the Fuchtbauer-Ladenburg theory validated the emission quality of the irradiated glasses. The quantum efficiency did not fall below 60% for all the doses. The color coordinates were clustered in the green region and showed not much variation with dose. The present study manifests the remarkable radiation hardness of the titled glass as a green emission device and laser.
... A number of publications reported the influence of γrays irradiation on optical absorption spectra of such materials [10][11][12]. However, only few works are devoted to the analysis of changes in the photoluminescence (PL) intensity under the action of γ-radiation, establishing the mechanism of the PL and the nature of radiation-induced defects at different radiation doses [13][14][15]. This especially applies to the analysis of crystal structures of chalcogenides doped with RE metals. ...
An erbium-doped β-GaLaS3 crystal has been grown by the solution-melt method, and the effect of γ-irradiation on their vibrational and radiative properties has been investigated. Experiments have demonstrated that the crystal is transparent in the near and mid-IR regions (transparency ∼62% in the range of 350 – 7100 cm-1), which allows it to be used as an effective matrix for creating lasers in this spectral range. For the first time, the vibrational spectrum of the crystal and the density of phonon states have been calculated using the DFT method. Both the original and γ -irradiated β-GaLaS3:Er crystals were investigated by Raman and IR spectroscopy. It has been established that irradiation with a dose of up to 5000 Gray does not lead to structural changes in the crystals. The effect of the formed defects is more clearly manifested in the IR reflection spectra, compared to the Raman spectra. The mechanism of the occurrence of excited states and the emission of Er ions embedded in the lattice has been established, and the effect of γ-irradiation on the radiative properties of β-GaLaS3:Er due to the occurrence of radiation-induced defects has been analyzed. A model has been constructed that explains the Stokes and anti-Stokes radiation of the erbium ions in the crystal. It has been demonstrated that the grown crystal has good prospects for sensor and laser technology of the near and mid-IR ranges due to relatively high values of optical transparency and the intense radiative capacity of the erbium ions.
... Studies on thin-film magnetic semiconductors are currently receiving worldwide attention due to their entirely new vital properties and the chances that they possess novel electronic, magnetic, and optical applications [1][2][3][4]. Magnetic semiconductors, which display rich interplay between magnetic cooperative phenomena and the semiconducting properties, are classical semiconductors where a controlled amount of the nonmagnetic component is substituted by transition metal or rare-earth metal [5,6]. Transition metal doping in the semiconductor also governs a new field of research called spintronics aiming to combine magnetic and semiconducting properties into a single material [7,8]. ...
Theoretical insights of the ultrasonic relaxation process in PbO–WO3–TeO2 glasses were investigated according to a model related to the propagation of ultrasonic waves in active two-well potential. The energy transfer of the ultrasonic waves either longitudinal or transverse to the glass network can create two-well potential based on the oxygen atoms displacements. The parameters of the model such as the mutual potential energy, the loss-centers, the prolongation or shrinkage of the double-well system, deformation potential were affected with the concentrations of the PbO. The number of loss centers was correlated to the compositional dependence of the elastic moduli on PbO content. The results showed that the degree of prolongation or shrinkage of the double-well system is affected with the concentration of PbO.
... Studies on thin-film magnetic semiconductors are currently receiving worldwide attention due to their entirely new vital properties and the chances that they possess novel electronic, magnetic, and optical applications [1][2][3][4]. Magnetic semiconductors, which display rich interplay between magnetic cooperative phenomena and the semiconducting properties, are classical semiconductors where a controlled amount of the nonmagnetic component is substituted by transition metal or rare-earth metal [5,6]. Transition metal doping in the semiconductor also governs a new field of research called spintronics aiming to combine magnetic and semiconducting properties into a single material [7,8]. ...
Novel magnetic semiconductors in bulk as well as in thin-film form are of great interest for spintronic device applications. Here, we report on the melt-quenched alloys of Mn-doped GeSe2 chalcogenide thin films deposited on microscopic glass substrates via the thermal evaporation. The optical properties of the thin films are investigated utilising the X-ray diffraction, and reflectance spectroscopy. Reflection spectroscopy data analysis shows that the deposited thin films are semiconducting, and the transitions are indirect. The values of optical band gap decrease from 2.03 to 1.58 eV with the Mn content. The disorder parameter shows a decrease with the Mn substitution. The addition of Mn in GeSe2 chalcogenide thin-film semiconductors shows an improvement in the linear and the nonlinear refractive index. The linear refractive index increases from 2.60 to 3.14 with the addition of Mn in GeSe2 chalcogenide thin-film semiconductors.
... Therefore, the study of PL is most commonly done for REdoped glasses and less often for single crystals. PL in chalcogenide glasses, compared to Er-doped single-crystalline semiconductors, exhibits a large number of bands in the visible and near IR ranges [11] which is due to the possibility of RE ions to occupy several positions in the amorphous matrix. It should be noted that single crystals are characterized by high intensity of PL but a small number of emission bands [3]. ...
The investigation of the properties of novel multicomponent chalcogenide single crystals is one of the principal directions of modern semiconductor optoelectronics. Particular attention is paid to the study of the photoluminescence properties of rare earth-doped chalcogenide semiconductors in the visible and near infrared range. This is due to the use of these materials in telecommunication devices, laser and sensor technology. We describe here the growth technique of the single crystal (Ga 69.5 La 29.5 Er) 2 S 300 composition by solution-melt method. X-ray diffraction methods confirm its crystallization in the space group Pna2 1 . Optical absorption spectrum of the single crystal in the visible and near infrared range was studied. Using the functional dependence of (αhν) ² on hν for direct transitions, the bandgap energy of the semiconductor was determined as 1.99 ± 0.01 eV. The increase in the dopant concentration from 0.2 to 0.4 at. % Er does not significantly change the band structure of the single crystal, therefore the bandgap energy is unchanged as well. Narrow absorption bands were recorded that are related to the transitions ⁴ I 15/2 → ⁴ I 11/2 , ⁴ I 15/2 → ⁴ I 9/2 , ⁴ I 15/2 → ⁴ F 9/2 in the f-shell of erbium ions. High concentration of energy levels in the band gap associated with the structure defects of the crystal results in the high value of the optical absorption coefficient. Photoluminescence excitation was achieved by a 532 nm (2.33 eV) laser at 150 mW. Intense Stokes photoluminescence bands were recorded at 1.53 and 0.805 eV, as well as lower-intensity maxima at 1.45, 1.27, 1.88 eV. These emission bands correspond to the transitions ⁴ I 9/2 → ⁴ I 15/2 , ⁴ I 13/2 → ⁴ I 15/2 , ⁴ S 3/2 → ⁴ I 13/2 , ⁴ I 11/2 → ⁴ I 15/2 , ⁴ F 9/2 → ⁴ I 15/2 in Er ³⁺ ions, respectively. An energy transition diagram for the f-shell of Er ³⁺ ions in the (Ga 69.5 La 29.5 Er) 2 S 300 single crystal was plotted. The emission mechanism and the important role of the cross-relaxation processes between the ground and excited states of Er ³⁺ ions were established. As a result of the influence of the local crystalline field on erbium ions, the Stark splitting of the ⁴ I 13/2 , ⁴ I 15/2 levels and the widening of the photoluminescence band with the maximum at 0.805 eV is observed. Intense infrared bands of the photoluminescence (1.53 and 0.805 eV) create prerequisites for using the (Ga 69.5 La 29.5 Er) 2 S 300 single crystal in sensor technology and optoelectronic devices.
... Thus, the PL intensity in the glasses is due to the emission of erbium ions which are uniformly distributed in the glass-forming matrix, as well as those which are located near the inhomogeneities and are involved in the formation of clusters. The study of static magnetization in the Ag 0.05 Ga 0.05 Ge 0.95 S 2 -Er 2 S 3 glasses [12] confirmed the formation of clusters. The calculated number of erbium ions in the cluster was estimated there as 1-1.5 Â 10 3 . ...
The monograph describes the technique of the synthesis of glasses and the
method of the growth of erbium-doped single crystals. The photoluminescence
spectra of Ag0.05Ga0.05Ge0.95S2-Er2S3 glasses and glasses from the Ga2S3-La2S3-Er2S3
system have been investigated in the visible and near-infrared ranges. According to
the energy transitions in the erbium ions, a radiation mechanism for conversion and
up-conversion luminescence has been established. The role of structural ordering
and the influence of defects on the radiation efficiency of Er3+ ions have been
investigated. The spectra of photoluminescence of (Ga54.59In44.66Er0.75)2S300 and
(Ga69.75La29.75Er0.5)2S300 single crystals have been studied. The efficiency of the
radiation of the amorphous and crystalline materials has been compared. Also, the
temperature dependence of the integral intensity of the radiation of glasses and
single crystals has been studied. It is established that in a limited temperature range,
these materials can be used for the manufacture of non-contact optical
thermosensors.
In this research work, we have done a systematic study of the influence of γ-irradiations on the parameters related to the optical characteristics of Se85Te9Ag6 nanochalcogenide thin films. The conventional melt quenching technique has been adopted for the synthesis of the bulk Se85Te9Ag6 alloy. The non-isothermal DSC measurements of Se85Te9Ag6 chalcogenide glasses were done for the confirmation of their glassy and amorphous nature. Thin films (40 nm) were deposited by the physical vapor condensation method on glass and Si substrates. γ-radiation of doses 5, 10, and 15 kGy was exposed on nano-thin films at a rate of 2 kGy hr−1. The JASCO UV/VIS/NIR spectrophotometer was used for optical studies of Se85Te9Ag6 nano-thin films. The optical measurement data confirms the indirect transition rule in the Se85Te9Ag6 glass. The observed value of the extinction coefficient and absorption coefficient has shown an increment with the dose of gamma radiation, whereas the increment in the crystal defects may lead to a decrement in the value of the estimated optical band gap.
In this work, bulk Se85Te15-xBix chalcogenide glasses were synthesized by melt quenching technique. The nano-thin chalcogenide films of Se85Te15-xBix alloys with thickness 40 nm were deposited on glass/Si wafer by Physical Vapour Condensation Technique (PVCT). Their optical and structural properties were analysed by the exposure of different gamma irradiation doses. High resolution X-ray diffraction (HRXRD) and field emission scanning electron microscopy (FESEM) were used to demonstrate the crystalline and morphological properties. The phase transformation studies of nano-thin films were carried out before and after irradiation by 3, 6, and 9 kGy doses of gamma (γ) rays. The optical parameters such as absorption coefficient, Urbach tail and extinction coefficient were found to be varied with the gamma irradiation doses. Importantly, the indirect allowed band gap increased as increasing the gamma irradiation doses. These notable shifts in the optical band gap and absorption coefficient values can be explained by the increment in disorderness and lattice strain due to gamma irradiation.
Erbium-doped chalcohalide glasses of systems were synthesized by using the melting-cooling method. The introduction of a halide component leads to a decrease in the absorption coefficient, and the addition of erbium leads to the emergence of narrow absorption bands associated with transitions in the f-shell of ions. Five PL bands were detected in erbium-doped samples when excited by a laser with a 532 nm wavelength, the most intense of which at 980 nm and 1540 nm are promising for use in optical amplifiers and fiber optic networks. It was established that the glass-forming matrix , doped with ions, is an effective light-emitting medium in the near-infrared range. At the same time, the concentration quenching of the PL was observed in the system when erbium content increases.
Preparation technology, the structure determination, multiband luminescence and nonlinear optical properties (NLO) of the chalcogenide glasses are subject of present work. The Ag0.05Ga0.05Ge0.95S2Er2S3 glass samples with two different 0.12 and 0.27 at.% Er content were prepared by classical two-stage melt-quenching method. Glass state and morphology were confirmed by X-ray and EDS techniques. Influence of the Erbium doping on the luminescence and NLO properties was investigated. Based on the diagram of energy levels for the Er3+ ions, we proposed a model that explains photoluminescence (PL) emission mechanism. It should be emphasized that investigated glasses (in comparison with other materials) are exceptional in that all bands of PL are intense due to small energy losses at excitation and emission of ions Er3+. The photoinduced second and third harmonic generations have been measured in the reflected geometry and compared with reference – BiB3O6 (BBO): 10%Nd crystal.
Electronic structure and optical properties were studied for novel (Ga70La30)2S300 and (Ga69.75La29.75Er0.5)2S300 single crystals synthesized by solution-melt technique. In particular, X-ray photoelectron spectroscopy (XPS) was used to measure core-level binding energies and valence-band spectra for as-synthesized and Ar⁺ ion-irradiated surfaces of these crystals. Presented XPS measurements show that the (Ga70La30)2S300 and (Ga69.75La29.75Er0.5)2S300 single crystals are rather stable in relation to Ar⁺ ion-irradiation. X-ray emission (XE) S Kβ1,3 and Ga Kβ2 bands were measured for the (Ga70La30)2S300 crystal giving information on the energy distribution of the S 3p and Ga 4p states, respectively. A comparison of these XE bands on a common energy scale with the XPS valence-band spectrum of (Ga70La30)2S300 indicates that the principal contribution of the S 3p and Ga 4p states occurs mainly at the top and in the central part of the valence band, respectively. In addition, optical absorption and photoluminescence spectra of the crystals were explored. Energy band gap values are estimated as 2.01 and 1.99 eV at room temperature for the (Ga70La30)2S300 and (Ga69.75La29.75Er0.5)2S300 crystals, respectively. Observed high-intensity green photoluminescence band when excited by a laser emitting at 810 nm suggests that the (Ga69.75La29.75Er0.5)2S300 crystal is a very attractive material for infrared to visible light conversion.
(Ga 55 In 45 ) 2 S 300 and (Ga 54.59 In 44.66 Er 0.75 ) 2 S 300 single crystals were successfully grown with the aim of exploring their potential for laser induced third harmonic generation (THG) and piezo-optical applications. Their Raman and luminescence spectra in the 150-300 K temperature range were studied. Influence of different gamma ray doses on the nonlinear optical properties were also explored. The optical properties of these crystals exhibit strong variation with temperature. It is concluded that (Ga 54.59 In 44.66 Er 0.75 ) 2 S 300 may be applied as promising materials for dosimetry applications in γ - radiation and optical temperature sensors.
The use of rare earths (RE) as dopant of materials has led the development of advanced materials for many applications such as optical tracers, special alloys, semiconductors, as well as radiation dosimeters. The development of new dosimetric materials based on REs is a great challenge in innovation of materials. Yttria (Y2O3) presents luminescent proprieties and is a promising material for radiation dosimetry. The present paper aims to evaluate paramagnetic defects of Y2O3 rods obtained via bio-prototyping by using Electron Paramagnetic Resonance (EPR) technique at room temperature. Ceramic rods were irradiated with gamma doses from 0.001 to 150kGy and evaluated by EPR at room temperature with X-band EPR. According to EPR results, as sintered samples exhibited an EPR signal with principal g tensor of 2.020 and maximum line width around 2.3mT, which is ascribed to interstitial oxygen ion. Dose response behaviour exhibited two distinct dose ranges, one is from 1 to 100Gy and the second is from 0.1 to 70kGy. Thermal annealing approaches reveal that defect centres of yttria decay significantly at high temperature. These innovative results make Y2O3 a promising material for radiation dosimetry.
In this article, we present the investigations of temperature dependent luminescence for the Ag0.05Ga0.05Ge0.95S2-Er2S3 glass system. The possibility to use temperature dependences of the photoluminescence of synthesized glasses for thermo sensors is considered. It is shown that logarithm of ratio of the integrated photoluminescence intensities for 980 and 600 nm (ln (I980/I660)) emission bands possess excellent linear dependence of temperature. At the same time, the nonlinear optical effects of two-photon absorption show substantial divergence from the sublinear dependences. These phenomena provide an opportunity to utilize Ag0.05Ga0.05Ge0.95S2-Er2S3 glasses for the fabrication of highly sensitive temperature sensor devices.
In this work study of photoluminescence (PL) spectra in the Er-doped glasses of the AgGaS2-GeS2 system is presented. Emission spectra of the glasses at T ≈ 292 K, excited by light with λex ≈ 980 nm and λex ≈ 532 nm are described well by transitions in the 4f-shell of Er3+ ions. Spectral curves of the emission can be deconvoluted into four Gaussian components. Er atoms are localized both in the glass matrix and (with increased concentration) around large structural damages (heterogeneities) which are drains for them. This causes broadening of the emission bands of Er3+ ions that are localized around heterogeneities. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
The density, molar volume, optical energy bandgap, and infrared absorption spectra in the range 400–4000 nm of borate glasses with composition 2xLi2O–xAl2O3–(1–3x)B2O3 (x varying from 0.10 to 0.18 mol fraction) prepared by conventional melt quench technique have been measured before and after successive γ-ray irradiation at the dose of 2.5 K Gy to elucidate the effect of gamma irradiation on such glasses. The radiation induced defects created by γ-ray and the changes in optical properties have been discussed.
Electron paramagnetic resonance (EPR) studies have been carried out on KU1 and KS-4V high purity quartz glasses and commercial silica Infrasil 301, irradiated with gamma rays up to a dose of 11.6MGy and neutron fluences of 1021 and 1022n/m2. Gamma irradiations produce a much higher concentration of defect centres (mainly E′, POR and NBOHC) for KU1 and I301 than for KS-4V silica. In contrast, neutron irradiation at the highest fluence produces similar concentrations in all silica types. These results agree to a good extent with those obtained in previous optical absorption measurements. Moreover, oxygen-related centres (POR and NBOHC) have been well characterized by means of electron paramagnetic resonance.
The effect of vacuum annealing on local structure reconstruction, evolution of photoluminescence (PL) and paramagnetic defects in carbon-rich a -Si 1-x C x: H films (x=0.7) was studied. Strong enhancement of visible (white-green) PL was observed after annealing in the temperature range of 400–500 ° C . Such enhancement was correlated with increasing of the concentration of carbon-hydrogen bonds in Si : C H n accompanied with increase in the fluctuation of the interatomic potential. Complete disappearance of PL, “graphitization” of the carbon precipitates, and a strong increase in the concentration of the paramagnetic states were observed after annealing at 650 ° C and above. The enhancement and the degradation of PL after different-temperature treatments are explained by the following competing effects: (1) enhancement of the radiative recombination due to passivation of paramagnetic defects with hydrogen and increase of localization of photoexcited electron-hole pairs due to formation of new Si:CH and (2) enhancement of the nonradiative recombination through the paramagnetic states due to increase in their concentration caused by graphitization of carbon precipitates after high- temperature treatment.
We report on photoluminescence (PL) properties of Er 3+ doped Ga 10 Ge 25 S 65 glass. Experiments were performed using 5 ns laser pulses at 980 nm (532 nm), in resonance with the 4 I 15/2→4 I 11/2 (4 I 15/2→2 H 11/2) transition of the Er 3+ ions. PL bands were observed from the blue to the near-infrared and the dependence of their intensity as a function of the laser intensity was analyzed. The PL temporal behavior was analyzed through rate equations for the population densities and using the Inokuti–Hirayama model. The results allowed identification of the PL pathways and the characterization of energy transfer processes involving pairs of ions.
The spectroscopic properties, structure and interconversions of optically active oxygen-deficiency-related point defects in vitreous silica are reviewed. These defects, the E′-centers (oxygen vacancies with a trapped hole or 3-fold-coordinated silicons), different variants of diamagnetic `ODCs' (oxygen-deficiency centers), and their Ge-related analogs play a key role in the fiber-optic Bragg grating writing processes. The controversy surrounding the structural models for the Si- and Ge-related ODCs is discussed and the similarity between the bulk and surface point defects in silica is emphasized. The possible interconversion mechanisms between 2-fold-coordinated Si, neutral oxygen vacancies and E′-centers are discussed. The effects of glassy disorder have a profound effect on defect properties and interconversion processes in silica.
Electron spin resonance (ESR) and thermally stimulated luminescence (TSL) spectra of the X -, γ-, and β- irradiated glasses with Ca3Ga2Ge3O12 (garnet) and Ca3Ga2Ge4O14 (Cagallogermanate) compositions as well as glass and ceramics with Ca3Ga2O6 composition are presented and analysed. The X- and γ-irradiation of Ge-contained glasses at room temperature induces simultaneously stable electron and hole paramagnetic defects, whereas the same irradiation of glasses with Ca3Ga2O6 composition induces exclusively stable hole paramagnetic defects. Electron defects are assigned to ensembles of the E' (Ge) centres with different local environments and hole defects belongs to an ensemble of O- centres, localized on different non-bridging oxygen of the glass network. TSL band, peaked at about 280 °C in the γ- and X - irradiated Ge-contained glasses is attributed to recombination of the E'(Ge) centres. TSL band with maximum about 230 °C in the γ- and X- irradiated Ge-contained glasses and glass and ceramics with Ca3Ga2O6 composition is related to recombination of the O- centres. TSL band, peaked at about 380 °C in the γ-, X- irradiated glasses and ceramics with Ca3Ga2O6 composition as well as bands, peaked at 120, 220, and 380 °C in the same β- irradiated samples are assigned to non-paramagnetic radiation defects. Activation energies for β- induced defects in the glass and ceramics with Ca3Ga2O6 composition are estimated.
Paramagnetic defects in erbium-doped γ-irradiated chalcogenide glasses were investigated by EPR method. Vacancy nature of defects and the dependence of their concentration on the irradiation dose and erbium content were determined. The measurement of the static magnetization revealed the presence of paramagnetic and ferromagnetic subsystems caused by isolated Er3+ ions and ion clusters, respectively. PL spectra of 4f–4f transitions of Er3+ ions and the radiation mechanism of γ-irradiated glasses were investigated. It was determined that PL intensity depends on the number of radiation induced defects and on the nature of the distribution of erbium which were determined by EPR and magnetic susceptibility.
Electron spin resonance (ESR), optical absorption spectra and photoluminescence spectra of Er3+ ions in soda-lime silicate glasses doped with different concentrations of Er2O3 have been studied. The glasses of the composition (in mol%) (65-x)SiO2:25Na2O:10CaO:xEr2O3 (where x=0.02, 0.05, 0.1, 0.3, 0.5, 1, 2, 3, 4 and 5) were prepared by the melt quenching method. ESR measurements were carried out at room temperature down to 1.62 K. Absorption spectra were investigated in the UV–VIS–NIR region from 300 to 1800 nm. Photoluminescence spectra were observed in the spectral range 500–800 nm under 514.5 nm argon-ion laser line excitation.
The absorption spectra and up-conversion luminescence of glassy alloys (100−X)Ag0.05Ga0.05Ge0.95S2–(X)Er2S3, where Х=0.42, 0.25, and 0.18 mol% (0.27; 0.16; and 0.12 at% Er, respectively) at excitation using diode laser with wavelength 980 nm in the range 450–1050 nm were investigated. We propose mechanism of emission in the glasses based on the model of intra-4f shell transitions in Er3+ ion. The influence of the formation of the structural units on the optical properties of the glasses using Raman spectroscopy that is important when designing the erbium-containing environments in laser technology was studied.
Electron spin resonance (ESR) and upconversion fluorescence spectra have been investigated for Er3+-doped Na2O–GeO2 glasses with molar compositions of xNa2O · (100 − x)GeO2 · 0.7Er2O3 prepared by the melt quenching method. The g-value for Er3+ derived from ESR spectrum and both the peak position and the integrated intensity of upconversion fluorescence spectra changed in the so-called germanate anomaly region of the glass. The upconversion fluorescence intensity correlated to the electron–phonon coupling strength.
This paper reviews half a century of research on radiation-induced point defects in pure and doped glassy silica and its crystalline polymorph α quartz, placing emphasis on trapped-electron centers because the vast majority of all presently known point defects in various forms of SiO2 are of the trapped-hole variety. The experimental technique most discussed here is electron spin resonance (ESR) because it provides the best means of identifying the point defects responsible for the otherwise difficult-to-attribute optical bands. It is emphasized that defects in α quartz have been unambiguously identified by exacting analyses of the angular dependencies of their ESR spectra in terms of the g matrix of the unpaired electron spin and the matrices of this spin's hyperfine interactions with non-zero-nuclear-spin 29Si and 17O nuclides in pure α quartz and/or with substitutional 27Al, 31P, or 73Ge in quartz crystals respectively doped with Al, P, or Ge. Many defects in pure and doped glassy silica can be unambiguously identified by noting the virtual identities of their spin Hamiltonian parameters with those of their far better characterized doppelgangers in α quartz. In fact, the Ge(1) trapped-electron center in irradiated Ge-doped silica glass is shown here to have a crystal-like nature(!), being virtually indistinguishable from the Ge(II) center in Ge-doped α quartz [R.J. McEachern, J.A. Weil, Phys. Rev. B 49 (1994) 6698]. Still, there are other defects occurring in glassy silica that are not found in quartz, and vice versa. Nevertheless, those defects in glasses without quartz analogues can be identified by analogies with chemically similar defects found in one or both polymorphs and/or by comparison with the vast literature of ESR of paramagnetic atoms and small molecules. Oxygen “pseudo vacancies” comprising trigonally coordinated borons paired with trigonally coordinated silicons were proposed to exist in unirradiated B2O3–3SiO2 glasses in order to account for observations of γ-ray-induced trapped-electron-type B- and Si-E′ centers [D.L. Griscom et al., J. Appl. Phys. 47 (1976) 960]. Analogous Al-E′ trapped-electron centers have been elucidated in silica glasses with Al impurities [K.L. Brower, Phys. Rev. B 20 (1979) 1799]). And it has been proposed [D.L. Griscom et al., J. Appl. Phys. 47 (1976) 960] that trapping of a second electron on such oxygen pseudo vacancies accounts for the predominant ESR-silent trapped-electron centers in irradiated silica glasses containing B or Al. The present paper additionally attempts to divine the identities of some of the ESR-silent radiation-induced trapped-electron centers in silica glasses free of foreign network-forming cations. This quest led to the doorstep of the most famous ESR-silent defect of all, the twofold-coordinated silicon, which is found only in silica glasses (not in quartz) and is responsible for the UV/visible optical properties of the oxygen-deficiency center known as ODC(II). The oxygen-deficiency center called ODC(I) is associated with an absorption band at 7.6eV and, though commonly believed to be a simple oxygen mono-vacancy, is clearly more complicated than that [e.g., A.N. Trukhin, J. Non-Cryst. Solids 352 (2006) 3002]. Certain well documented but persistently enigmatic ODC(I)↔ODC(II) “interconversions” [reviewed by L. Skuja, J. Non-Cryst. Solids 239 (1998) 16] have never been explained to universal satisfaction. An innovative combined ESR/thermo-stimulated-luminescence (TSL) study of a series of pure low-OH silica glasses with oxygen deficiencies of 0.000, ~0.015, and ~0.030vol.% [A.N. Trukhin et al., J. Non-Cryst. Solids, 353 (2007) 1560] places new constraints on all future models for ODC(II). Taking this history into account, specific redefinitions of both ODC(I) and ODC(II) are proposed here. The present review also revisits a study of X-ray-induced point defects in an ultra-low-OH, high-chlorine but otherwise ultra-high-purity silica glass [D.L. Griscom, E.J. Friebele, Phys. Rev. B34 (1986) 7524], arguing that (1) most of the reported E′γ and E′δ centers were created via the mechanism of dissociative electron capture at chlorine-decorated oxygen vacancies, (2) the concomitantly created interstitial chloride ions serve as ESR-silent trapped-electron traps, (3) the ESR-detected “Cl0” centers arise from hole trapping on O3≡Si–Cl units without detachment of the resulting Cl atom, and (4) those chlorine atoms that are detached by homolytic bond fission are ESR-silent. Finally, in chlorine-free, low-OH, high-purity silica glasses, up to 100% of the trapped-electron centers appear to be ESR silent and are tentatively ascribed to electron trapping in pairs below the mobility edge of the conduction band. In such cases, the sum of all trapped-hole centers has been found to decay exponentially with increasing isochronal annealing temperature in the range 100 to ~300K [D.L. Griscom, Nucl. Inst. & Methods B46 (1990) 12]. Overall, this review consolidates a large amount of long-existing but often underappreciated knowledge bearing on the natures of trapped-electron centers in pure and doped glassy silica, proposes new models for some of these, and raises a number of questions that cannot be fully answered without future performance of new experiments and/or ab initio calculations.
The influence of annealing temperature Ta on the optical absorption edge in the previously γ-irradiated glasses of Ge–Sb(As)–S ternaries of pseudobinary ‘stoichiometric’ Sb(As)2S3–GeS2 and non-stoichiometric Sb(As)2S3–Ge2S3 cut-sections is studied. It is established that the post-irradiation thermally produced changes of the optical absorption edge differ in various Ta regions. Threshold restoration effects are found beginning from some intermediate onset temperature Ton for all investigated glasses. Compositional features of the apparent activation energies determined in corresponding Ta regions are analyzed. A possible mechanism for the observed effects is discussed.
The efficiency of up-conversion luminescence of Er3+ ions (excited by laser light operating at 810 nm) in the GeS2–Ga2S3:Er2S3 system strongly depends on the energy position of the fundamental absorption edge. This dependence is due to non-radiative energy exchange between the electronic subsystem of the glassy matrix and excited levels of Er3+ ions. In chalcogenide glasses Ge and Ga atoms are fourfold coordinated. Except for the M (M=Ge, Ga)–S heterobonds, the rest are M–M homobonds. These homobonds can be detected with Raman spectroscopy. The energy position of the absorption tail of the fundamental band depends on the concentration of M–M homobonds. When the concentration of these bonds increases the absorption edge shifts to longer wavelengths and the intensity of up-conversion luminescence decreases. The relative concentration of M–M bonds depends not only on composition of the glassy matrix but also on the synthesis and on concentration of extrinsic impurities such as OH−, SH− and –CH2–. Another cause of reduction of up-conversion luminescence intensity is the inhomogeneous distribution of REI in the Ga2S3–GeS2 glasses. The simple model describing dependence of luminescence intensity on type of REI distribution in the glassy matrix is discussed.
The up-conversion fluorescence excited with 813 and 1550 nm light is investigated in glasses of the Ga2S3–GeS2–Er2S3 system. The influence of the glassy matrix composition and Er concentration on the luminescence and absorption spectra is studied. Increasing the Ga content relative to Ge decreases the erbium concentration quenching effect. The efficiency of up-conversion fluorescence has a strong dependence on thermal history of the sample. Annealing of the glasses and decreasing the synthesis temperature increase the luminescence intensity.
Intrinsic paramagnetic responses were observed in the 60TeO2–25ZnO–15Na2O and 85TeO2–15Na2O mol% glasses, after γ-irradiation at room temperature: (1) a shoulder at g1 = g∥ = 2.02 ± 0.01 and an estimated g⊥ ~ 2.0 attributed to tellurium–oxygen hole center (TeOHC); (2) a narrow resonance at g2 = 1.9960 ± 0.0005 related to the modifiers and (3) a resolved resonance at g3 = 1.9700 ± 0.0005 ascribed to a tellurium electron center (TeEC) of an electron trapped at an oxygen vacancy (VO+) in a tellurium oxide structural center. It is suggested that the creation of (NBO−,VO+) pair follows a mechanism where the modifier oxide molecule actuates as a catalyser. An additional model for the NBO radiolysis produced by the γ-irradiation is proposed on the basis of the evolution of the g1, g2 and g3 intensities with increasing dose (kGy).
In the present work γ-irradiation induced optical band gap variations (ΔEopt) were investigated on Ge–As–Se and Ge–As–Se–Te chalcogenide glasses. Higher doses of γ-irradiation resulted in decreased Eopt, which was composition dependent. Especially, glasses with stoichiometric compositions showed different ΔEopt from nonstoichiometric glasses under the same irradiation conditions. There seemed existence of a threshold Eopt (TE) under the certain dose of irradiation below which ΔEopt hardly occurred. Results were interpreted from viewpoint of glass structure, Chemical Bond Approach (CBA) and localized states density theory. Raman analysis supported well these discussions.
Rare Earth Metals and Alloys. North-Holland
- S Legvold
Legvold, S., 1980. Rare Earth Metals and Alloys. North-Holland, Amsterdam.
Electron paramagnetic resonance study of Mn 2 þ , Cu 2 þ and VO 2 þ in Li 2 0-Na 2 O-B 2 O 3 glasses
- M V Ramana
- K Siva Kumar
- Rahman
- Suresh Syed
- D Babu
- S G Sathyanarayan
- G S Sastry
Ramana, M.V., Siva Kumar, K., Rahman, Syed, Suresh Babu, D., Sathyanarayan, S.G.,
Sastry, G.S., 1989. Electron paramagnetic resonance study of Mn 2 þ, Cu 2 þ and
VO 2 þ in Li 2 0-Na 2 O-B 2 O 3 glasses. J. Mater. Sci. Lett. 8, 1471-1473.
- S V Vonsovsky
Vonsovsky, S.V., 1971. Magnetism. Nauka, Moscow (Russian language).
Physical Values: Handbook
- A P Babichev
- N A Babushkina
- N A Bratkovsky
Babichev, A.P., Babushkina, N.A., Bratkovsky, N.A., et al., 1991. Physical Values:
Handbook. Energoatomizdat, Moscow (Russian language).
Role of structural ordering on optical properties of the glasses Ag 0.05 Ga 0.05 Ge 0.95 S 2 -Er 2 S 3
- V V Halyan
- V V Strelchuk
- V O Yukhymchuk
- A H Kevshyn
- G Davydyuk
- Ye
- M V Shevchuk
- S V Voronyuk
Halyan, V.V., Strelchuk, V.V., Yukhymchuk, V.O., Kevshyn, A.H., Davydyuk, G.Ye,
Shevchuk, M.V., Voronyuk, S.V., 2013. Role of structural ordering on optical
properties of the glasses Ag 0.05 Ga 0.05 Ge 0.95 S 2 -Er 2 S 3. Phys. B: Condens. Matter
411, 35-39.